1. Field of the Invention
The present invention relates to a backlight unit, and more particularly, to a backlight unit including a condensing film on which hetero-conic lenses are two-dimensionally arranged to improve brightness and viewing angle characteristics.
2. Description of the Related Art
Liquid crystal displays (LCDs) are passive devices that cannot generate light and thus require backlight units as light sources. Due to the influence of the recent emphasis on environmentally-friendly technology, more attention is being paid to products having improved brightness characteristics while consuming the same or less electricity than related art products. Thus, a great deal of research into improving the bright characteristics of backlight units has been undertaken.
A common method used in the related art to improve the brightness of backlight units is to use condensing films such as prism sheets and lenticular sheets. Particularly, it is known that brightness characteristics can be markedly improved by using a stack of two prism sheets. In this case, however, viewing angle characteristics are deteriorated, although brightness characteristics can be improved. Use of a stack of two or three semispherical micro-lens array sheets is considered to prevent such a deterioration in viewing angle characteristics. However, brightness characteristics cannot be improved to satisfactory levels through only the semispherical micro-lens array sheets.
That is, what is needed are condensing sheets (films) that can sufficiently improve both the brightness and viewing angle of liquid crystal displays.